Chemical Inhibition of the Mitochondrial Division Dynamin Reveals Its Role in Bax/Bak-Dependent Mitochondrial Outer Membrane Permeabilization (original) (raw)
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Human Molecular Genetics
The purpose of our study was to better understand the effects of mitochondrial-division inhibitor 1 (Mdivi-1) on mitochondrial fission, mitochondrial biogenesis, electron transport activities and cellular protection. In recent years, researchers have found excessive mitochondrial fragmentation and reduced fusion in a large number of diseases with mitochondrial dysfunction. Therefore, several groups have developed mitochondrial division inhibitors. Among these, Mdivi-1 was extensively studied and was found to reduce dynamin-related protein 1 (Drp1) levels and excessive mitochondrial fission, enhance mitochondrial fusion activity and protect cells. However, a recent study by Bordt et al. (1) questioned earlier findings of the beneficial, inhibiting effects of Mdivi-1. In the current study, we studied the protective effects of Mdivi-1 by studying the following: mRNA and protein levels of electron transport chain (ETC) genes; mitochondrial dynamics and biogenesis genes; enzymatic activities of ETC complexes I, II, III and IV; the mitochondrial network; mitochondrial size & number; Drp1 GTPase enzymatic activity and mitochondrial respiration (1) in N2a cells treated with Mdivi-1, (2) overexpressed with full-length Drp1 + Mdivi-1-treated N2a cells and (3) Drp1 RNA silenced+Mdivi-1-treated N2a cells. We found reduced levels of the fission genes Drp1 and Fis1 levels; increased levels of the fusion genes Mfn1, Mfn2 and Opa1; and the biogenesis genes PGC1α, nuclear respiration factor 1, nuclear respiratory factor 2 and transcription factor A,
Mitochondrial fission - a drug target for cytoprotection or cytodestruction?
Pharmacology Research & Perspectives, 2016
Mitochondria are morphologically dynamic organelles constantly undergoing processes of fission and fusion that maintain integrity and bioenergetics of the organelle: these processes are vital for cell survival. Disruption in the balance of mitochondrial fusion and fission is thought to play a role in several pathological conditions including ischemic heart disease. Proteins involved in regulating the processes of mitochondrial fusion and fission are therefore potential targets for pharmacological therapies. Mdivi-1 is a small molecule inhibitor of the mitochondrial fission protein Drp1. Inhibiting mitochondrial fission with Mdivi-1 has proven cytoprotective benefits in several cell types involved in a wide array of cardiovascular injury models. On the other hand, Mdivi-1 can also exert antiproliferative and cytotoxic effects, particularly in hyperproliferative cells. In this review, we discuss these divergent effects of Mdivi-1 on cell survival, as well as the potential and limitations of Mdivi-1 as a therapeutic agent.
Cell Death and Differentiation, 2007
Most cell death stimuli trigger the mitochondrial release of cytochrome c and other cofactors that induce caspase activation and ensuing apoptosis. Apoptosis is also associated with massive mitochondrial fragmentation and cristae remodeling. Dynaminrelated protein 1 (Drp1), a protein of the mitochondrial fission machinery, has been reported to participate in apoptotic mitochondrial fragmentation. Several theories explaining the mechanisms of cytochome c release have been proposed. One suggests that it relies on the activation of Drp1-mediated mitochondrial fission. Here, we report that downregulation of Drp1 inhibits fragmentation of the mitochondrial network and partially prevents the release of cytochrome c but fails to prevent the release of other mitochondrial factors such as second mitochondria-derived activator of caspase/direct IAP-binding protein with low pI, Omi/HtrA2, adenylate kinase 2 and deafness dystonia peptide/TIMM8a. An explanation for the prevention of cytochrome c release is provided by our observation that inhibiting Drp1-mediated mitochondrial fission prevents the mitochondrial release of soluble OPA1 that was proposed to regulate cristae remodeling and complete cytochrome c release during apoptosis. Finally, we observed that downregulation of Drp1 delays but does not inhibit apoptosis, suggesting that mitochondrial fragmentation is not a prerequisite for apoptosis.
A novel Drp1 inhibitor diminishes aberrant mitochondrial fission and neurotoxicity
Excessive mitochondrial fission is associated with the pathology of a number of neurodegenerative diseases. Therefore, inhibitors of aberrant mitochondrial fission could provide important research tools in addition to potential leads for drug development. Using a rational approach, we designed a novel and selective peptide inhibitor, P110, of excessive mitochondrial fission. P110 inhibits Drp1 enzyme activity and blocks Drp1/Fis1 interaction in vitro and in cultured neurons, whereas it has no effect on the interaction between Drp1 and other mitochondrial adaptors, as demonstrated by co-immunoprecipitation. Furthermore, using a model of Parkinson’s disease (PD) in culture, we demonstrated that P110 is neuroprotective by inhibiting mitochondrial fragmentation and reactive oxygen species (ROS) production and subsequently improving mitochondrial membrane potential and mitochondrial integrity. P110 increased neuronal cell viability by reducing apoptosis and autophagic cell death, and reduced neurite loss of primary dopaminergic neurons in this PD cell culture model. We also found that P110 treatment appears to have minimal effects on mitochondrial fission and cell viability under basal conditions. Finally, P110 required the presence of Drp1 to inhibit mitochondrial fission under oxidative stress conditions. Taken together, our findings suggest that P110, as a selective peptide inhibitor of Drp1, might be useful for the treatment of diseases in which excessive mitochondrial fission and mitochondrial dysfunction occur.
A Small Molecule Promotes Mitochondrial Fusion in Mammalian Cells
Angewandte Chemie International Edition, 2012
Mitochondria are highly dynamic cellular organelles that continuously undergo fission and fusion. [1] This dynamic nature plays a key role in regulating mitochondrial function, and also gives mitochondria their heterogeneous morphology. [2] Disruption of the balance between mitochondrial fusion and fission, especially a shift towards fission, contributes to a variety of human disorders, including neurodegenerative disease, metabolic disease, and ischemia. [3] In addition, fragmented mitochondria are early signs of activation of apoptosis, [4] and fusion of mitochondria by genetic or chemical manipulation has been shown to have an anti-apoptotic effect. [5] Thus, the identification of small molecules that modulate mitochondrial dynamics can provide useful tools to study mitochondrial function and may ultimately lead to new therapeutics. Here, we report the identification and preliminary biological characterization of the small molecule, M1, which significantly restores the mitochondrial tubular network in response to genetically or chemically induced fragmentation. Mitochondrial fusion is a two-step process in which the outer and inner mitochondrial membranes (OMM and IMM, respectively) fuse separately, but in an ordered fashion. [6] The core components of the mitochondrial fusion machinery are the OMM proteins, mitofusin 1 and 2 (Mfn1 and Mfn2), and the IMM protein, optic atrophy 1 (Opa1). [7] Unlike
Mitochondrial division inhibitor (mdivi-1) decreases oxidative metabolism in cancer
British Journal of Cancer
Background Previous studies suggested that mdivi-1 (mitochondrial division inhibitor), a putative inhibitor of dynamin-related protein (DRP1), decreased cancer cell proliferation through inducing mitochondrial fusion and altering oxygen consumption. However, the metabolic reprogramming underlying the DRP1 inhibition is still unclear in cancer cells. Methods To better understand the metabolic effect of DRP1 inhibition, [U-13C]glucose isotope tracing was employed to assess mdivi-1 effects in several cancer cell lines, DRP1-WT (wild-type) and DRP1-KO (knockout) H460 lung cancer cells and mouse embryonic fibroblasts (MEFs). Results Mitochondrial staining confirmed that mdivi-1 treatment and DRP1 deficiency induced mitochondrial fusion. Surprisingly, metabolic isotope tracing found that mdivi-1 decreased mitochondrial oxidative metabolism in the lung cancer cell lines H460, A549 and the colon cancer cell line HCT116. [U-13C]glucose tracing studies also showed that the TCA cycle intermedi...
Activation of mitochondrial fusion provides a new treatment for mitochondria-related diseases
Biochemical pharmacology, 2018
Mitochondria fragmentation destabilizes mitochondrial membranes, promotes oxidative stress and facilitates cell death, thereby contributing to the development and the progression of several mitochondria-related diseases. Accordingly, compounds that reverse mitochondrial fragmentation could have therapeutic potential in treating such diseases. BGP-15, a hydroxylamine derivative, prevents insulin resistance in humans and protects against several oxidative stress-related diseases in animal models. Here we show that BGP-15 promotes mitochondrial fusion by activating optic atrophy 1 (OPA1), a GTPase dynamin protein that assist fusion of the inner mitochondrial membranes. Suppression of Mfn1, Mfn2 or OPA1 prevents BGP-15-induced mitochondrial fusion. BGP-15 activates Akt, S6K, mTOR, ERK1/2 and AS160, and reduces JNK phosphorylation which can contribute to its protective effects. Furthermore, BGP-15 protects lung structure, activates mitochondrial fusion, and stabilizes cristae membranes i...
Inhibiting the Mitochondrial Fission Machinery Does Not Prevent Bax/Bak-Dependent Apoptosis
Molecular and Cellular Biology, 2006
Apoptosis, induced by a number of death stimuli, is associated with a fragmentation of the mitochondrial network. These morphological changes in mitochondria have been shown to require proteins, such as Drp1 or hFis1, which are involved in regulating the fission of mitochondria. However, the precise role of mitochondrial fission during apoptosis remains elusive. Here we report that inhibiting the fission machinery in Bax/Bak-mediated apoptosis, by down-regulating of Drp1 or hFis1, prevents the fragmentation of the mitochondrial network and partially inhibits the release of cytochrome c from the mitochondria but fails to block the efflux of Smac/DIABLO. In addition, preventing mitochondrial fragmentation does not inhibit cell death induced by Bax/Bak-dependent death stimuli, in contrast to the effects of Bcl-xL or caspase inhibition. Therefore, the fission of mitochondria is a dispensable event in Bax/Bak-dependent apoptosis.
Cell Death Discovery
Maintenance of mitochondrial integrity is critical for normal cellular homoeostasis. Most cells respond to stress stimuli and undergo apoptosis by perturbing mitochondrial structure and function to release proteins, such as cytochrome c, which are essential for the execution of the intrinsic apoptotic cascade. Cancer cells evade these events by overexpressing the anti-apoptotic BCL-2 family of proteins on mitochondrial membranes. Inhibitors of the antiapoptotic BCL-2 family proteins, also known as BH3 mimetics, antagonise the pro-survival functions of these proteins and result in rapid apoptosis. Although the precise mechanism by which BH3 mimetics induce apoptosis has been well characterised, not much is known in terms of the structural changes that occur in mitochondria during apoptosis. Using a panel of highly selective BH3 mimetics and a wide range of cell lines, we demonstrate that BH3 mimetics induce extensive mitochondrial fission, accompanied by swelling of the mitochondrial matrix and rupture of the outer mitochondrial membrane. These changes occur in a BAX/ BAK-dependent manner. Although a major mitochondrial fission GTPase, DRP-1, has been implicated in mitochondrial apoptosis, our data demonstrate that DRP-1 might function independently/downstream of BH3 mimetic-mediated mitochondrial fission to facilitate the release of cytochrome c and apoptosis. Moreover, downregulation of DRP-1 prevented cytochrome c release and apoptosis even when OPA1, a protein mediating mitochondrial fusion, was silenced. Although BH3 mimetic-mediated displacement of BAK and other BH3-only proteins from BCL-X L and MCL-1 was unaffected by DRP-1 downregulation, it prevented BAK activation significantly, thus placing DRP-1 as one of the most critical players, along with BAX and BAK, that governs BH3 mimetic-mediated cytochrome c release and apoptosis.